Lime cleaning process to remove manganese oxide
AssigneeAluminum Company of America
InventorsPaul J. The, William V. Felix
Life of this patent
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Abstract
A process for cleaning lime having undesirable levels of contaminants, particularly manganese oxide, is disclosed. The process includes leaching the contaminants from the lime with an aqueous means, preferably spent Bayer liquor, to form a slurry containing said impurities and cleaned lime. The cleaned lime is then removed from the slurry containing the contaminants.
Claims18
A process for removing manganese oxide from lime comprising
- leaching the manganese oxide from the lime with sodium aluminate liquor produced by the Bayer process to form a slurry containing said manganese oxide and leached lime;
- and
- removing the leached lime from the slurry containing manganese oxide.
A process for the production of alumina from sodium aluminate liquor resulting from caustic leaching of an alumina-bearing source material comprising
- (a) heating said sodium aluminate liquor;
- (b) digesting the heated sodium aluminate liquor under pressure;
- (c) gradually bringing the sodium aluminate liquor back to atmospheric pressure;
- (d) reducing the iron content of the sodium aluminate liquor by adding lime to the sodium aluminate liquor after said sodium aluminate liquor has been brought back to atmospheric pressure, said lime having been leached with spent Bayer liquor to remove manganese oxide therefrom prior to being added to said sodium aluminate liquor, said lime also having contained at least 0.27 weight percent manganese oxide prior to said leaching;
- (e) separating solids from the sodium aluminate liquor after bringing said sodium aluminate liquor back to atmospheric pressure;
- and
- (f) precipitating aluminum trihydroxide from the separated sodium aluminate liquor.
A process for the production of alumina from sodium aluminate liquor resulting from caustic leaching of an alumina-bearing source material comprising
- (a) heating said sodium aluminate liquor;
- (b) digesting the heated sodium aluminate liquor under pressure;
- (c) gradually bringing the sodium aluminate liquor back to atmospheric pressure;
- (d) filtering solids from the sodium aluminate liquor after bringing the sodium aluminate liquor back to atmospheric pressure;
- (e) increasing the filtration rate of said solids from the sodium aluminate liquor by adding lime to the sodium aluminate liquor being filtered so as to form a mixture with said solids having less specific surface area for filtering than said solids would have had without having added said lime, said reduced specific surface area increasing said filtration rate, said lime having been leached with spent Bayer liquor to remove manganese oxide therefrom prior to being added to said sodium aluminate liquor, said lime also having contained at least 0.27 weight percent manganese oxide prior to said leaching;
- and
- (f) precipitating aluminum trihydroxide from the sodium aluminate liquor remaining after filtering said solids therefrom.
Dependencies are inferred from the claim text.